Portable computer docking units have been marketed as devices that allow the user to have the advantages of a portable computer without any of the portable computer's limitations, at least when operating at the user's desk or other primary work location.
In the typical implementation, the docking unit is located at the user's office. The docking unit has a docking bay for receiving and providing electrical connections to the portable computer. The docking unit may also have a bus extension that electrically mates with the portable computer's bus when it is in the docking bay and a number of expansion slots to hold hard drives, CD-ROMs, modems etc., which are not found in the portable computer. As a result, when the portable computer is installed in the docking unit, its minimalist portable computer capabilities are augmented and extended to those that are typically found in most desktop or non-portable computer systems. In this way, the user has the advantages associated with the portable computer while not losing the functionality that would otherwise be available from a desktop computer system.
Most docking units also have port replication functionality. Many times the portable computer will be outfitted with a variety of communication ports, including serial ports, parallel ports, universal serial bus ports (USB), video ports, RJ45 network ports, etc. These ports are accessed through port connectors, usually on the back of the computer. It is typical for the docking unit to have a similar array of port connectors so that when the portable computer is connected to the docking unit, the portable computer's communication ports are tied to the analogous port connectors in the docking unit. In the parlance of the industry, the portable computer's communication ports are replicated in the docking unit. The advantage of this system is that the user can connect such components as a network interface, full size keyboard, mouse, and full size monitor to the port connectors of the docking unit. The docked portable computer thus connects to these various devices, but the mere act of undocking the portable computer serves to disconnect the computer from these various devices, in one step.
Some docking units are intended primarily as port replicators. These devices will not have the bus extensions, and consequently, the expansion slots, to support additional active bus devices for the portable computer. Instead, they are primarily intended to perform the port replication function. While obviously not having all of the advantages associated with the more elaborate docking units, port replicators provide the user with many of the core advantages of a desktop docking unit, such as the possibility of using a full size keyboard and desktop monitor and offering these features at a reasonable price point in a system with a small footprint.